This application is based on Japanese Patent Application No. 9-318164, filed Nov. 19, 1997, the contents of which are incorporated herein by reference.
The present invention relates to a video information recording/reproduction system for recording video information composed of digital video information on a disk storage medium and reproducing video information from the disk storage medium.
In recent years, recording/reproduction systems for recording and reproducing so-called multimedia information such as digital video information or still image, audio information, and character information are extensively developed. Particularly, a DVD (Digital Video Disk) drive using a DVD as a storage medium has received a great deal of attention. The DVD drive includes a read-only DVD-ROM drive and a DVD-RAM drive which allow recording and reproduction.
In particular, the DVD-RAM drive has not only a function of reproducing multimedia information recorded on the DVD in advance but also a function of recording digital video information transmitted from, e.g., a digital broadcasting station. The DVD-RAM drive has therefore received attention as not only a video player or videocassette recorder for reproducing video information on the screen of a television receiver but also an external storage device for a personal computer. The DVD-RAM drive is a promising storage medium incorporated in an apparatus such as a set top box or IRD (Integrated Receiver Decoder) which has a digital satellite broadcasting receiver (including an antenna) and displays received digital video information on the display (screen) of a television receiver or personal computer.
Using the recording/reproduction function of the DVD-RAM relatively easily realizes an edit function of editing video information recorded on the DVD-RAM. The video information edit function is to cut (remove) desired frame information included in full-motion video continuously reproduced on the screen of the television receiver or the like, and to extract desired frame information into another video information. Realizing this edit function requires a function capable of editing desired frame information in full-motion video in units of frames (or units of pictures) designated by the user.
Video information recorded on the DVD-RAM is generally encoded (compressed) by a moving picture coding scheme called MPEG (Moving Picture coding Experts Group) 2. This MPEG2 scheme employs a so-called GOP (Group Of Pictures) structure. The GOP structure is used to process video data as an access unit obtained by grouping a plurality of pictures (frames), and is generally composed of about 15 frames (reproduction time: about 0.5 sec).
One GOP is composed of a predetermined number of pictures of a plurality of picture types (to be referred to as picture data hereinafter). The picture type means the type of encoded image and includes three types of pictures, i.e., an I picture (Intracoded image), a P picture (Predictive coded image), and a B picture (Bidirectionally predictive coded image). The I picture is frame information which can be decoded independently of another type of picture data (without any preceding and succeeding frame information). The P picture is frame information which can be decoded using difference information from the I picture. The B picture is frame information which can be decoded using difference information from the preceding I picture and difference information from the succeeding P picture. That is, the P and B pictures except for the I picture are encoded images which cannot be decoded by themselves.
As described above, editing digital video information using the DVD-RAM requires a function capable of editing the information in units of frames (or units of pictures) designated by the user. However, in the recording/reproduction system employing the MPEG2 scheme, when the video data process unit (i.e., coding unit) is the GOP, a position within the GOP may be designated as a reference position for dividing video information. More specifically, when video information (continuous reproduction data unit including a GOP header) composed of a plurality of GOPs is divided at a desired position, a picture within a given GOP may be designated as a division boundary.
The GOP is composed of a plurality of picture types of picture data, as described above. When, e.g., the former half of video data is cut (removed) at a designated division position, the start picture in the latter half of the video data may be a P or B picture. Since the P or B picture cannot be independently decoded, video information including the latter half of the video data causes a reproduction error. If the start picture is an I picture, the video information can be reproduced without any problem. Namely, in the system wherein video data is processed in units of GOPs, like the MPEG2 scheme, the data can be easily edited in units of GOPs but cannot be practically edited in units of pictures within the GOP.
It is an object of the present invention to provide a video information recording/reproduction system capable of, when video information composed of GOP-unit video data is to be edited, dividing the video information using a division position designated within a GOP and improving the video information edit function regardless of the type of picture corresponding to the division position.
More specifically, the present invention is used for a recording/reproduction system having a function of recording video information having a data structure such as a GOP structure in the MPEG2 scheme on a disk recording medium, and reproducing video information from the disk recording medium. This system comprises setting means for setting frame information designated by the user on the screen as a reference position for dividing the video information reproduced on the screen of the display. The setting means allows to set the reference position within the GOP serving as access unit video data. The setting means comprises a command input function for an editing process.
This system further comprises determination means for determining the picture type of start picture data starting from the reference position set within the GOP by the setting means. The determination means determines whether the picture type of start picture data is the I type. Upon reception of the determination result, change means changes the picture data to I picture data when the start picture data is not of the I type. More specifically, when the start picture data is of the I type, the change means does not change the picture data. Edit means of this system edits GOP video data composed of one video data portion including the I picture data obtained by the change means and the other video data portion. In this system, when the other video data portion is included in video information to be cut, it is changed to reproduction invalid data which cannot be a target to be reproduced.
According to the recording/reproduction system of the present invention, in an editing process of cutting part of video information processed as continuous reproduction data, even if the cut position (reference position for division) is within the GOP, the start picture at the cut position can be set to an I picture which can always be independently decoded. Even if part of the GOP is included in video data to be cut, video data starting from the cut position can be reproduced. Therefore, in editing video information in units of GOPs composed of a plurality of picture types of picture data, the cut position can be freely set. Even if the cut position is within the GOP, an editing process of using necessary video data and cutting unnecessary video data can be easily realized.
According to another aspect of the present invention, the system comprises copy means for copying GOP video data set by the setting means in a predetermined area of the disk storage medium. Using the copy means can decode the edited GOP video data to original video data. An original GOP composed of cut video data and edited video data within the GOP can be decoded to decode video information before edition.
According to the present invention, in the digital video information recording/reproduction system using, e.g., a DVD-RAM, particularly when the scheme employing the MPEG2 picture coding and GOP structure is applied, video information can be divided at a division position designated within the GOP regardless of the type of picture at the division position. When video information composed of GOP-unit video data is edited, an editing process within the GOP can be realized, thereby improving the video information edit function.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.